Moving Movement Detectors

Abstract

Single nerve cells readily recordable in the ventral nerve cord of locusts and crickets respond to moving targets but not to the forced movement of the eye. This asymmetry of response is shown to be due to an inhibition generated whenever large areas of the hemispheric receptive fields of these units are stimulated. Dimming of a large, stationary target movement of a large field of vertical bars, or movement of the eye while viewing a large pattern are all potent inhibitory stimuli which can prevent the cell's otherwise vigoious response to a small target or arrest a response which is already under way. These properties of single insect neurons are phenomenologically similai to human sensations described by psychophysicists as saccadic suppression and backward masking, as well as to the properties of some vertebrate visual neurons. It is argued that the spatial and dynamic characteristics of neurons in visual input pathways may well acount for some psychophysical findings generally interpreted in terms of central mechanisms such as “efference copy,” and must be incorporated inmodels seeking to explain perceptual stability during eye movement.